I think the nastier stuff won't happen until Iran is in a really bad situation. Maybe they could fire an advanced missile and strike Israel's Dimona nuclear facility or carry out drone attacks inside the US. It's easy to sneak drones around and assemble them, so I think we can expect attacks far away from the battlefield.

One thing I'll disagree with is this idea that sleeper cells will appear from no-where and massacre people at bars and nightclubs. It doesn't seem like it's Iran's style - they'd rather hit a military base with a drone.

Remember that while Iran's command structure is ruined, they can still command operations globally through their intelligence officers.